Shell Programming and Scripting

m1xram, you are misunderstanding Wikipedia, I'm afraid.

The article/subsection I linked to says there are two interpretations of the term "steep learning curve". The first is yours, which says basically: "you can learn a lot about X quickly".

The second interpretation ( which is more common, and is how people usually use the phrase ) says basically: "how long until i get X mastered or mostly mastered or a real good grip on, etc.?".

In common parlance, people would say that the learning curve of Chess is much steeper than that of Checkers or Tic-Tac-Toe because there is more to learn about Chess, and much more to learn to "master" it.

The learning curve on the phrase "learning curve" is steeper than I had previously thought

I guess a practical example that I built in bash might help, it reads in a text file called ll a line at a time (with latitude/longitude) and finds nearest city and country code from the web.

Code:

cat "${@:-$ll}" |
        while read i
        do
                ref_num=$(($ref_num+1))
                lat=`echo $i | awk -F ';' '{print $1}'`
                lon=`echo $i | awk -F ';' '{print $2}'`
                url="http://ws.geonames.org/findNearbyPlaceName?lat=$lat&lng=$lon"
                                curl -s "$url" > xmlfile
                                city=`/usr/bin/xmlstarlet sel -t -m //geoname -v toponymName xmlfile`
                                country_code=`/usr/bin/xmlstarlet sel -t -m //geoname -v countryCode xmlfile`
                                mysql -u $USER_NAME --password=$PASSWORD -D "somedb" -e \
                                        "INSERT INTO somedb.sometable (id, ref_num, timestamp, lat, \
                                        lon, city, country_code) \
                                        VALUES (NULL,'$ref_num','$lat','$lon',\
                                        '$city','$country_code')";
        done

what kinds of things would I have to learn to build this in perl?

Ever Read XKCD? Check this out: xkcd: Geohashing

here's a Perl Script that implements the algorithm in the comic:

Code:

#! /usr/bin/perl

use strict;
use warnings;

use LWP::Simple;
use URI::Escape;

use Finance::Quote;
use Digest::MD5;
use Math::BigInt;

my $begin_from = join '', @ARGV if @ARGV;

my $q = Finance::Quote->new;
my %dow = $q->fetch( 'nyse', '^DJI' );
my $hashthis = $dow{'^DJI', 'isodate'} . '-' . $dow{'^DJI', 'open'};
printf "DOWDATE: %s\n", $hashthis;

my $o = Digest::MD5->new;
$o->add( $hashthis );
my $hash = $o->hexdigest;
printf "MD5: %s\n", $hash;

my $x = '.' . substr ( Math::BigInt->from_hex ( '0x' . substr $hash, 0, 16), 0, 6);
my $y = '.' . substr ( Math::BigInt->from_hex ( '0x' . substr $hash, 16, 16), 0, 6);
my $addr = $begin_from || '100 S. Market St., Frederick MD';
$addr = uri_escape( $addr );
my $str = get( "http://rpc.geocoder.us/service/csv?address=$addr" );
( my $start_lat, my $start_long ) = split /,/, $str;
printf "START COORDS: %s %s\n", $start_lat, $start_long;

$start_lat =~ /(.+?)\..+$/; my $new_lat_pref = $1;
$start_long =~ /(.+?)\..+$/; my $new_long_pref = $1;
my $geohash = $new_lat_pref . $x . ' ' . $new_long_pref . $y;
printf "GEOHASH: %s\n", $geohash;

In addition to getting Lat-Long Coords, it also fetchs Real-Time Stock quotes, and runs some fairly solid crytpographic hashing algorithms....

Perl won't be usable as a login shell.
It's negative. The more you know, the more damage you do to your project overall productivity
Depends on what power you measure.
Any other language is probably a better choice than Perl (ok, I'm too extreme here).
php is fine. python would be easier to build than perl.

Write my Geohash Code in Python in Fewer lines and/or so that it executes more quickly. and post please. No copying. The XKCD Geohash is a well known exercise, by now. and we will see. Where's you evidence for such grandiose and unfriendly statements.

You Just say "Perl Sucks" and repeat that 5 times, but don't give any examples; or rebuff any of the the actual specific strong points that three other posters listed here.

More over you general smugness towards Perl thumbs it's nose at literally tens of thousands of people who have added to the Perl extrodinary effort community. PHP and Ruby would not exist were it not for Perl. Perl was the first platform agnostic, run your code on anything byte machine and pioneered so much of what we expect from a high-level language today.

By the way you can make a Perl program your login shell. Just look on CPAN at the Term:: space, for one. /bin/plsh

One of the plusses I saw for perl was the depth and breadth of perl code out there in the world, which must, one can surmise, account for its usefulness. I'm just trying to pick from python/perl now that I know it can do most of what I want it to do. It sounds like perl might be a little more versatile still (from what I'm hearing) for both scripting on up through web apps?

UncleCameron: Yes. This is an excellent point, and you stated clearly. One of the great advantages of Perl is that it can go toe-to-toe with awk and sed for command-line work; toe-to-toe with BASH/KSH/etc.. for system scripts; go toe-to-toe with PHP for web development; and go toe-to-toe with Python and even Java for Full-Fledged Systems Development.

That versatility is perhaps Perl's greatest strength. I can write any awk one-liner just as quickly and efficiently with perl. I can write a cronjob or the like just quickly and effciently as Shell. I can write a web app just as quickly and efficiently as PHP or Ruby. And I can even write very large scale systems stuff that will run with Java any day.

What other tool has such flexibilty? None. Detractors of Perl will say it tries to be everything and fails at each of it. They never seem to back it up. Perl One-Liners are ofter *better* than awk; perl scripts are almost always better than their BASH equivalent. Perl Web App are often better than their PHP or Python equivalents. etc. And there is massive proof for this.

Moreover. Perl has the most *dedicated and caring community* of all programming languages. As I mentioned before, no language has had as many smart and talented people give so much of their time willingly.

Perl 6 has struggled to say the least and went off track. Perl6 really *did* bite off a bit too much and has lacked a direction. We should all be running it now, in a perfect world. As a result Perl fell off in some important new areas of practical computing like MVC. Too many people care passionately about Perl to let this go on, and are working everyday to fix it.

Frankly, I am extremely disappointed with the moderator's post, in which he engaged in straight up "Linux vs. BSD vs. WIndows" type discussion with no substance and plenty of misplaced condescension. I hope his colleagues will give him a warning for a clear violation his own forum's rules

( I'm just sick to death of hearing Perl sucks and is useless; when it is runs a significant percent of the entire world's financial transactions. ) Barclays, BofA, Credit Suisse, and others all Use Perl; )